a. Field
The present disclosure relates to a magnetic field generator with relatively thin magnetic field transmitters configured to, among other things, minimally occlude a fluoroscopic image.
b. Background
A wide variety of medical devices may be inserted into the body to diagnose and treat various medical conditions. Catheters, for example, are used to perform a variety of tasks within human bodies and other bodies, including the delivery of medicine and fluids, the removal of bodily fluids, and the transport of surgical tools and instruments. In the diagnosis and treatment of atrial fibrillation, for example, catheters may be used to deliver electrodes to the heart for electrophysiological mapping of the surface of the heart and to deliver ablative energy to the surface of the heart.
Catheters are typically routed to a region of interest through the body's vascular system. In a conventional catheterization, a micro-puncture needle (e.g., a Seldinger needle) is used to puncture the skin surface to gain access to, for example, a femoral artery, and a guide wire is then inserted through the needle before the needle is removed. A catheter sheath with a dilator inserted in it is then inserted over the guide wire. The dilator and the guide wire are then removed, leaving the sheath in place in the femoral artery. The sheath has an inner diameter greater than the outer diameter of a catheter to be used in the procedure. The catheter is then inserted into the sheath, and the sheath and/or catheter are subsequently threaded through the vasculature to a region of interest. Typically, but not necessarily, the catheter is then moved longitudinally relative to the sheath so as to extend from the distal end of the sheath to the region of interest. The longitudinal movement may be done either manually by a clinician or through the use of electromechanical drive systems.
It is desirable to track the position of medical devices such as catheters as they are moved within the body so that, for example, drugs and other forms of treatment are administered at the proper location and medical procedures can be completed more efficiently and safely. One conventional means to track the position of medical devices within the body is fluoroscopic imaging. Fluoroscopy is disadvantageous, however, because it subjects the patient and physician to undesirable levels of electromagnetic radiation. As a result, medical device navigation systems have been developed to track the position of medical devices within the body. These systems typically rely on the generation of electrical or magnetic fields and the detection of induced voltages and currents on position sensors attached to the medical device and/or external to the body. The information derived from these systems is then provided to a physician through, for example, a visual display. Oftentimes, a representation of the medical device is displayed relative to a computer model or one or more images (including, but not limited to, fluoroscopic images) of the anatomical region in which the device is being maneuvered. In order to display the medical device at the correct location relative to the model or image, the model or image must be registered within the coordinate system of the navigation system.
Magnetic field transmitters may be used in conjunction with a medical device navigation system. The transmitters within the navigation system can be installed in a variety of ways. If the imaging system used to capture the images is physically integrated with the navigation system, as described in commonly assigned U.S. Published Patent Application No. 2008/0183071 A1, the entire disclosure of which is incorporated herein by reference, the transmitters can be installed such that they will not be in the path of the x-ray beam. The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.